Titanium alloys



United States Patent TITANIUM ALLOYS Earl F. Swazy, Richard Freyer, and Lee S. Busch, Indianapolis, Ind'., assignors, by mesne assignments, to Mallory-Sharon Titanium Corporation, Indianapolis, Ind., a corporation of Delaware No Drawing. Application September 4, 1953, Serial No. 382,183, now Patent No. 2,786,756, dated March 26, 19 57, which is a division of application Serial No. 138,516, January 13, 1950, now Patent No. 2,661,286, dated December 1, 1953. Divided and this application February 15, 1957, Serial No. 644,432

3 Claims. (Cl. 75--175.5)

This invention reates generally to alloys of titanium and has particular reference to alloys consisting of tit-anium, carbon and silicon, alone, or in combination with another element, to form a quaternary alloy with titanium predominating. This application is a divisional application of Serial No. 382,183, filed September 4, 1953, now Patent No. 2,786,756, dated March 26, 1957, which in turn is a division of application Ser. No. 138,516, filed January 13, 1950, now Patent No. 2,661,286, dated December 1, 1953.

An object of thepresent invention, therefore, is to provide Wrought, ductile alloys of titanium.

Another object of the present invention is to provide a wrought, ductile alloy of titanium, carbon and silicon.

Still another object of the invention is to provide quaternary alloys of titanium.

Yet another object of the invention is to provide alloys of titanium consisting of titanium, carbon and silicon having greater resistance to oxidation at elevated temperatures than pure titanium and exhibiting good hardness characteristics thereof.

Another object of the invention is to provide an alloy of titanium consisting of titanium, carbon and silicon and any one of the following elements: aluminum, copper, vanadium, chromium, boron, tungsten and iron.

Yet another object of the invention contemplates a method of preparing quaternary alloys of titanium consisting of the ternary alloys of carbon, silicon and titanium, to which is added an element from the group; aluminum, copper, chromium, vanadium, boron, tungsten or IIOII.

The invention, in another of its aspects, relates to the novel features and principles teaching the objects of the invention and to the novel principles employed herein Whether or not these features and principles may be used in said object or in said field.

It is found that alloys of titanium, silicon and carbon with titanium predominating as a ternary alloy, or as an alloy to which may be added another element such as aluminum, chromitun, copper, vanadium, boron, tungsten or iron provide a resistance to oxidation at elevated temperatures greater than that of pure titanium. Such alloys provide ductile, strong alloys of titanium and exhibit good corrosion resistance and high hardness characteristics at elevated temperatures. These alloys are usually manufactured by melting and casting in a graphite retort under an inert or neutral atmosphere; for example, argon, or in a vacuum. Further, the alloys may also be prepared by powder metallurgy methods. Thus, as an example, alloys containing .l% to silicon, .2% to 2% carbon with the balance titanium, as compared to pure titanium, are characterized by having a higher tensile strength, equivalent ductility, slightly higher electrical resistivity, much better resistance to oxidation at elevated temperatures and high hardness at temperatures up to 600 C. Further .992% Sili- .477% Carcom-.47% bon-Bal- Carbonance Tita- Balance nium Titanium Ultimate Tensil Strength p. s. i 105, 000 121,600 Elongation in 2 percent 1 .5 12. 5: Resistivity "ohm-c1115.- 65x10 76. 5X10 Moreover, alloys, such, as above, are characterized by a unique response to heat treatment. Upon quenching,

from 1000 CL, these alloys do not harden appreciably (most alloys of titanium which contain metals forming st'able carbides db harden on quenching). However, as the tensile strength is lowered to 113,50'0' 1 s. i., the elongat'ion increases to 16.5%. In the as forged condition, the hardness of 600" C. increases from 0 Rockwell A to 32 Rockwell A when quenched. These changes are apparently caused by the presence of large amount of B titanium (body centered cubic) which is not transformed to a on fast cooling from 1000 C.

Again, in resistance to sealing tests at 900 C., an alloy containing 992% silicon was three times as effective as that for titanium containing .47% carbon. The results revealed a 536% increase in weight for the silicon alloy and 1.89% for the titanium alloy containing carbon only.

A base alloy of titanium, silicon and carbon may be combined with the element,'iron, to form a new quaternary alloy titanium, iron, silicon and carbon. These alloys of titanium, iron, silicon, and carbon are ductile and provide alloys of titanium which are stronger than titanium and have better resistance to oxidation at elevated temperatures. These alloys further exhibit better corrosion resistance and high hardness at elevated temperatures than those of pure titanium.

These alloys are characterized by adequate ductility even though the ductility is less than that of pure titanium. Moreover, the alloys of this invention are susceptible to hardening by quenching in Water or other media. Alloys in the quenched state have ultimate tensile strengths of approximately 175,000 p. s. i. and elongation in 2" of about 4%.

The alloys of this invention containing iron may be manufactured by melting and casting under an inert or neutral atmosphere (for example, argon) or in a vacuum. The alloys may also be prepared by powder metallurgy methods. A preferred method consists of mixing iron and silicon in massive or powder form with titanium in sponge or powder form and melting and casting in graphite. Since the source of the carbon is the crucible the amount is easily controlled by varying the time the charge is molten. The alloys are preferably forged in air at temperatures between 800 C. to 900 C. but may be hot or cold worked by the usual methods known to the art.

The alloys herein described may be made containing small but significant amounts of iron, silicon and carbon; that is, up to 10% iron; up to 5% silicon; up to 2% carbon; and the balance titanium. The lower limit is 0.1% iron; 0.1% silicon; 0.1% carbon; and the balance titanium. A practical range of composition is 1% to 5% iron, 1% to 3% silicon, 0.3% to 0.7% carbon and the balance titanium."

Alloys of iron prepared according to this invention exhibit substantially the following minimum properties:

As Hot Quenched Forged from Ultimate Tensile Strength 130, 000 175, 000 Elongation in 2" l0 3 Modulus of Elastic p. s. i 18x10 21x10 Electrical Resistivity... ohm-cm 75x10 75x10- The following chart is useful in depicting the constituents of the above described alloys.

Alloy table Ti, per- Si, per 0, per- Alloy cent cent cent and- (1 Ti, Si, o 99. 7-88 0.1-10 0. 2-2 (8) Ti, Si, 0 Fe 99. 783 1-5 1-2 01-10% Fe.

stantially all titanium. A quaternary alloy may consist of up to 10% silicon; up to 2% carbon; and up to 10% iron; the remainder being substantially all titanium.

While the present invention as to its objects is merely illustrative and not exhaustive in scope and since many widely different embodiments of the invention may be made without departing from the scope thereof, it is intended that all matter contained in the above description be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. Alloys containing from 0.1% to 10% iron, from 0.1% to 5% silicon, from 0.1% to 2% carbon, and the balance thereafter being substantially all titanium.

2. Alloys containing from 0.1% to 5% iron, from 0.1% to 3% silicon, from 0.1% to 2% carbon, and the balance being substantially all titanium, said alloys being quench hardenable.

3. Alloys of titanium as in claim 2 having the following minimum properties:

No references cited. 

1. ALLOYS CONTAINING FROM 0.1% TO 10% IRON, FROM 0.1% TO 5% SILICON, FROM 0.1% TO 2% CARBON, AND THE BALANCE THEREAFTER BEING SUBSTANTIALLY ALL TITANIUM. 